There is a plethora of references (both patents and literature articles) dealing with the formation of intermediate oxidation products, such as diacids, for example, one of the most important being adipic acid. Adipic acid is used to produce Nylon 66 fibers and resins, polyesters, polyurethanes, and miscellaneous other compounds.
There are different processes of manufacturing adipic acid. The conventional process involves a first step of oxidizing cyclohexane with oxygen to a mixture of cyclohexanone and cyclohexanol (KA mixture), and then oxidation of the KA mixture with nitric acid to adipic acid. Other processes include, among others, the "Hydroperoxide Process," the "Boric Acid Process," and the "Direct Synthesis Process," which involves direct oxidation of cyclohexane to adipic acid with oxygen in the presence of solvents, catalysts, and initiators or promoters.
Initiators or promoters are presently being used to shorten considerably an induction period at the beginning of the reaction. Accepted explanations, which have been given regarding the role of the initiators or promoters, involve oxidation of the catalyst, which is usually cobaltous ions to cobaltic ions.
The Direct Synthesis Process has been given attention for a long time. However, to this date it has found little commercial success. One of the reasons is that although it looks very simple at first glance, it is extremely complex in reality. Due to this complexity, one can find strikingly conflicting results, comments, and views in different references.
It is well known that after a reaction has taken place according to the Direct Synthesis, a mixture of two liquid phases is present at ambient temperature, along with a solid phase mainly consisting of adipic acid. The two liquid phases have been called the "Polar Phase" and the "Non-Polar" phase. However, no attention has been paid so far to the importance of the two phases, except for separating the adipic acid from the "Polar Phase" and recycling these phases to the reactor partially or totally with or without further treatment. Further, no attention has been paid to the behavior of catalyst, such as solubility, for example, during reaction conditions.
It is also important to note that most, if not all, studies on the Direct Oxidation have been conducted in a batch mode, literally or for all practical purposes.
There is a plethora of references dealing with oxidation of organic compounds to produce acids, such as, for example, adipic acid.
The following references, among the plethora of others, may be considered as representative of oxidation processes relative to the preparation of diacids.
U.S. Pat. No. 5,463,119 (Kollar) discloses a process for the oxidative preparation of C.sub.5 -C.sub.8 aliphatic dibasic acids by
(1) reacting, PA1 (2) removing the aliphatic dibasic acid; and PA1 (3) recycling intermediates, post oxidation components, and derivatives thereof remaining after removal of the aliphatic dibasic acid into the oxidation reaction. PA1 (1) reacting, at a cycloaliphatic hydrocarbon conversion level of between about 7% and about 30%, PA1 (2) isolating the C5-C8 aliphatic dibasic acid. PA1 (a) feeding continually into a reaction zone an oxidant and a rate-modulator in the presence of a catalyst and a solvent, under conditions causing oxidation of the hydrocarbon to the dibasic acid by the oxidant, the hydrocarbon and the rate-modulator being fed at a first ratio, the solvent comprising an organic acid containing only primary and/or secondary hydrogen atoms; and PA1 (b) adjusting said first ratio in a manner that the oxidation rate falls within a range of desired values. PA1 (a) partially oxidizing cyclohexane to a second mixture comprising cyclohexanone, the second mixture having a desired second ratio of cyclohexane to cyclohexanone; PA1 (b) feeding the mixture into a reaction zone in the presence of a catalyst, a solvent and an oxidant, and under conditions causing formation of adipic acid; PA1 (c) adjusting said desired second ratio in a manner that the oxidation rate falls within a desired range. PA1 a major reaction chamber; PA1 first feeding means for feeding into the major reaction chamber the cycloaliphatic hydrocarbon; PA1 second feeding means for feeding continually into the major reaction chamber an oxidation rate-modulator; PA1 third feeding means for feeding into the major reaction chamber an oxidant; PA1 fourth feeding means for feeding into the major reaction chamber a catalyst and a solvent, the solvent comprising an organic acid containing only primary and/or secondary hydrogen atoms; PA1 condition controlling means for controlling conditions in the major reaction chamber in a manner to induce oxidation of the hydrocarbon by the oxidant; PA1 ratio adjusting means for causing the hydrocarbon and the rate-modulator to be fed into the major reaction chamber at a first ratio, and PA1 optionally adjusting said first ratio in a manner that the oxidation rate falls within a range of desired values. PA1 a precursory reaction chamber; PA1 first cyclohexane feeding means for feeding cyclohexane into the precursory reaction chamber; PA1 first oxidant feeding means for feeding an oxygen containing gas into the precursory reaction chamber in order to partially oxidize the cyclohexane to a second mixture comprising cyclohexanone, the second mixture having a desired second ratio of cyclohexane to cyclohexanone; PA1 a major reaction chamber; PA1 second mixture feeding means for feeding the second mixture into the major reaction chamber; PA1 additional feeding means for feeding one or more of a catalyst, a solvent and an oxidant into the major reaction chamber; PA1 condition controlling means for controlling conditions in the major reaction chamber in a manner to induce oxidation of the hydrocarbon by the oxidant; and PA1 ratio adjusting means for adjusting said second ratio in a manner that the oxidation rate falls within a range of desired values. PA1 a preceding reaction chamber; PA1 first feeding means for feeding into the preceding reaction chamber the cycloaliphatic hydrocarbon; PA1 second feeding means for feeding continually into the preceding reaction chamber a oxidation rate-modulator; PA1 third feeding means for feeding into the preceding reaction chamber an oxidant; PA1 fourth feeding means for feeding into the preceding reaction chamber a catalyst and a solvent, the solvent comprising an organic acid containing only primary and/or secondary hydrogen atoms; PA1 a major reaction chamber connected to the preceding reaction chamber in a manner that contents of the preceding reaction chamber may move to the major reaction chamber; PA1 means for maintaining the temperature of the preceding reaction chamber higher than the temperature of the major reaction chamber; and PA1 ratio adjusting means for causing the hydrocarbon and the rate-modulator to be fed to the preceding reaction chamber at a first ratio, and optionally adjusting said first ratio in a manner that the oxidation rate in the major reaction chamber falls within a range of desired values.
(a) at least one saturated cycloaliphatic hydrocarbon having from 5 to 8 ring carbon atoms in the liquid phase and PA2 (b) an excess of oxygen gas or an oxygen-containing gas in the presence of PA2 (c) a solvent comprising an organic acid containing only primary and/or secondary hydrogen atoms and PA2 (d) at least about 0.002 mole per 1000 grams of reaction mixture of a polyvalent heavy metal catalyst; PA2 (a) at least one saturated cycloaliphatic hydrocarbon having from 5 to 8 ring carbon atoms in the liquid phase and PA2 (b) an excess of oxygen gas or an oxygen containing gas mixture in the presence of PA2 (c) less than 1.5 moles of a solvent per mole of cycloaliphatic hydrocarbon (a), wherein said solvent comprises an organic acid containing only primary and/or secondary hydrogen atoms and PA2 (d) at least about 0.002 mole per 1000 grams of reaction mixture of a polyvalent heavy metal catalyst; and
U.S. Pat. No. 5,374,767 (Drinkard et al.) discloses formation of cyclohexyladipates in a staged reactor, e.g. a reactive distillation column. A mixture containing a major amount of benzene and a minor amount of cyclohexene is fed to the lower portion of the reaction zone and adipic acid is fed to the upper portion of the reaction zone, cyclohexyladipates are formed and removed from the lower portion of the reaction zone and benzene is removed from the upper portion of the reaction zone. The reaction zone also contains an acid catalyst.
U.S. Pat. No. 5,321,157 (Kollar) discloses a process for the preparation of C.sub.5 -C.sub.8 aliphatic dibasic acids through oxidation of corresponding saturated cycloaliphatic hydrocarbons by
U.S. Pat. No. 5,221,800 (Park et al.) discloses a process for the manufacture of adipic acid is disclosed. In this process, cyclohexane is oxidized in an aliphatic monobasic acid solvent in the presence of a soluble cobalt salt wherein water is continuously or intermittently added to the reaction system after the initiation of oxidation of cyclohexane as indicated by a suitable means of detection, and wherein the reaction is conducted at a temperature of about 50.degree. C. to about 150.degree. C. at an oxygen partial pressure of about 50 to 420 pounds per square inch absolute.
U.S. Pat. No. 3,987,100 (Barnette et al.) describes a process of oxidizing cyclohexane to produce cyclohexanone and cyclohexanol, said process comprising contacting a stream of liquid cyclohexane with oxygen in each of at least three successive oxidation stages by introducing into each stage a mixture of gases comprising molecular oxygen and an inert gas.
U.S. Pat. No. 3,957,876 (Rapoport et al.) describes a process for the preparation of cyclohexyl hydroperoxide substantially free of other peroxides by oxidation of cyclohexane containing a cyclohexane soluble cobalt salt in a zoned oxidation process in which an oxygen containing gas is fed to each zone in the oxidation section in an amount in excess of that which will react under the conditions of that zone.
U.S. Pat. No. 3,932,513 (Russell) discloses the oxidation of cyclohexane with molecular oxygen in a series of reaction zones, with vaporization of cyclohexane from the last reactor effluent and parallel distribution of this cyclohexane vapor among the series of reaction zones.
U.S. Pat. No. 3,530,185 (Pugi) discloses a process for manufacturing precursors of adipic acid by oxidation with an oxygen-containing inert gas which process is conducted in at least three successive oxidation stages by passing a stream of liquid cyclohexane maintained at a temperature in the range of 140.degree. to 200.degree. C. and a pressure in the range of 50 to 350 p.s.i.g. through each successive oxidation stage and by introducing a mixture of gases containing oxygen in each oxidation stage in an amount such that substantially all of the oxygen introduced into each stage is consumed in that stage thereafter causing the residual inert gases to pass countercurrent into the stream of liquid during the passage of the stream through said stages.
U.S. Pat. No. 3,515,751 (Oberster et al.) discloses a process for the production of epsilon-hydroxycaproic acid in which cyclohexane is oxidized by liquid phase air oxidation in the presence of a catalytic amount of a lower aliphatic carboxylic acid and a catalytic amount of a peroxide under certain reaction conditions so that most of the oxidation products are found in a second, heavy liquid layer, and are directed to the production of epsilon-hydroxycaproic acid.
U.S. Pat. No. 3,361,806 (Lidov et al.) discloses a process for the production of adipic acid by the further oxidation of the products of oxidation of cyclohexane after separation of cyclohexane from the oxidation mixture, and more particularly to stage wise oxidation of the cyclohexane to give high yields of adipic acid precursors and also to provide a low enough concentration of oxygen in the vent gas so that the latter is not a combustible mixture.
U.S. Pat. No. 3,234,271 (Barker et al.) discloses a process for the production of adipic acid by the two-step oxidation of cyclohexane with oxygen. In a preferred embodiment, mixtures comprising cyclohexanone and cyclohexanol are oxidized. In another embodiment, the process involves the production of adipic acid from cyclohexane by oxidation thereof, separation of cyclohexane from the oxidation mixture and recycle thereof, and further oxidation of the other products of oxidation.
U.S. Pat. No. 3,231,608 (Kollar) discloses a process for the preparation of aliphatic dibasic acids from saturated cyclic hydrocarbons having from 4 to 8 cyclic carbon atoms per molecule in the presence of a solvent which comprises an aliphatic monobasic acid which contains only primary and secondary hydrogen atoms and a catalyst comprising a cobalt salt of an organic acid, and in which process the molar ratio of said solvent to said saturated cyclic hydrocarbon is between 1.5:1 and 7:1, and in which process the molar ratio of said catalyst to said saturated cyclic hydrocarbon is at least 5 millimoles per mole.
U.S. Pat. No. 3,161,603 (Leyshon et al.) discloses a process for recovering the copper-vanadium catalyst from the waste liquors obtained in the manufacture of adipic acid by the nitric acid oxidation of cyclohexanol and/or cyclohexanone.
U.S. Pat. No. 2,565,087 (Porter et al.) discloses the oxidation of cycloaliphatic hydrocarbons in the liquid phase with a gas containing molecular oxygen and in the presence of about 10% water to produce two phases and avoid formation of esters.
U.S. Pat. No. 2,557,282 (Hamblet et al.) discloses production of adipic acid and related aliphatic dibasic acids; more particularly to the production of adipic acid by the direct oxidation of cyclohexane.
U.S. Pat. No. 2,439,513 (Hamblet et al.) discloses the production of adipic acid and related aliphatic dibasic acids and more particularly to the production of adipic acid by the oxidation of cyclohexane.
U.S. Pat. No. 2,223,494 (Loder et al.) discloses the oxidation of cyclic saturated hydrocarbons and more particularly to the production of cyclic alcohols and cyclic ketones by oxidation of cyclic saturated hydrocarbons with an oxygen-containing gas.
U.S. Pat. No. 2,223,493 (Loder et al.) discloses the production of aliphatic dibasic acids and more particularly to the production of aliphatic dibasic acids by oxidation of cyclic saturated hydrocarbons with an oxygen-containing gas.
German Patent DE 44 26 132 A 1 (Kysela et al.) discloses a method for dehydration of process acetic acid from the liquid-phase oxidation of cyclohexane with air, in the presence of cobalt salt as a catalyst after separation of the adipic acid by filtration and the cyclohexane phase by phase separation, while simultaneously avoiding cobalt salt precipitates in the dehydration column, characterized in that the acetic acid phase to be returned to the beginning of the process is subjected to azeotropic distillation by the use of added cyclohexane, under distillative removal of the water down to a residual content of less than about 0.3 to 0.7 wt %.
PCT Demand International Publication WO 96/03365 (Costantini et al.) discloses a method of recycling a cobalt-containing catalyst in a reaction involving the direct oxidation of cyclohexane into adipic acid using an oxygen containing gas. The method is characterized in that the reaction mixture, obtained in a preceding stage where the cyclohexane was oxidized into adipic acid, of which at least part of the intermediate oxidation products, such as cyclohexanol and cyclohexanone, the carboxylic acid and water has been separated and of which at least part of the adipic acid formed has been recovered by crystallization, undergoes at least one extraction operation using at least one cosolvent or a mixture comprising a cosolvent and a carboxylic acid. The method is also characterized by the separation of a mixture containing at least part of the cobalt catalyst, part of the carboxylic acid and optionally residual quantities of other compounds and a solution containing the co-solvent and at least part of the glutaric and succinic acids formed during the oxidation reaction, and the carboxylic acid.
None of the above references, or any other references known to the inventors disclose, suggest or imply, singly or in combination, oxidation of cyclic hydrocarbons to dibasic acids in the presence of initiators by adjusting the ratio of hydrocarbon to initiator, subject to the intricate and critical controls and requirements of the instant invention as described and claimed.
Our co-pending application, Docket No. T-603, of Mark W. Dassel, Eustathios Vassiliou, David C. DeCoster, Ader M. Rostami, and Sharon M. Aldrich, titled "Methods and Devices for Controlling the Reaction Rate of a Hydrocarbon to an Acid by Making Phase-related Adjustments," filed on Mar. 6, 1997, and having a Ser. No. 08/812,847, is also incorporated herein by reference.
Our co-pending application, Docket No. T-701, of Mark W. Dassel, David C. DeCoster, Ader M. Rostami, Sharon M. Aldrich, and Eustathios Vassiliou, titled "Methods and Devices for Preparing Dibasic Acids," filed on Mar. 27, 1997, and having a Ser. No. 08/824,992 is also incorporated herein by reference.
All of the following patent applications, which were filed simultaneously with the present application are also incorporated herein by reference:
Docket No. U.S. patent application Ser. No. 08/859,985 of Eustathios Vassiliou, Mark W. Dassel, David C. DeCoster, Ader M. Rostami, and Sharon M. Aldrich, titled "Methods and Devices for Controlling the Reaction Rate of a Hydrocarbon to an Intermediate Oxidation Product by Pressure Drop Adjustments";
Docket No. U.S. patent application Ser. No. 08/861,281 of Mark W. Dassel, Eustathios Vassiliou, David C. DeCoster, Ader M. Rostami, and Sharon M. Aldrich, titled "Methods and Devices for Controlling the Reaction Rate of a Hydrocarbon to an Intermediate Oxidation Product by Monitoring Flow of Incoming and Outcoming Gases";
Docket No. U.S. patent application Ser. No. 08/861,176 of Mark W. Dassel, Eustathios Vassiliou, David C. DeCoster, and Ader M. Rostari, titled "Methods of Preparing an Intermediate Oxidation Product from a Hydrocarbon by Utilizing an Activated Initiator";
Docket No. U.S. patent application Ser. No. 08/859,890 of Ader M. Rostami, Mark W. Dassel, Eustathios Vassiliou, David C. DeCoster, titled "Methods and Devices for Controlling the Oxidation of a Hydrocarbon to an Acid by Regulating Temperature/Conversion Relationship in Multi-Stage Arrangements"; and
Docket No. U.S. patent application Ser. No. 08/861,210 of Eustathios Vassiliou, Ader M. Rostami, David C. DeCoster, and Mark W. Dassel, titled "Pseudo-Plug-Flow Reactor".